In various prior patents, there have been discussions of the modification of the surface charge of vascular systems or substances to be used in association therewith. Generally, it has been suggested that such systems be dealt with to make the surface charge thereof more negative to avoid thrombosis and the like.
A variety of hemostatic agents are known such as Gelfoam.TM. manufactured by Up-John and disclosed in U.S. Pat. No. 2,465,357; Avitene.TM. manufactured by Acecon and disclosed in U.S. Pat. No. 3,742,955 and Surgicell.TM. manufactured by Johnson and Johnson and disclosed in U.S. Pat. No. 3,364,200.
Battista et al in Patent 3,742,955 report that collagen in various treated or prepared forms is useful in surgery and for the treatment of wounds, and that E. Peacock, Jr. et al Ann. Surg. 161,238-47, February, 1965 teaches that collagen has hemostatic properties when used as a wound dressing. Battista et al further report that it has been found that fibrous collagen and fibrous products derive from collagen when properly prepared and when wet with blood will not only demonstrate hemostasis, but also demonstrates an unexpected adhesiveness to severed biological surfaces in warm blooded animals. They also provide a method of preparing finely divided fibrous collagen and fibrous products derived from collagen which are useful hemostatic agents and have unique adhesive properties in contact with a severed biological surface in a warm blooded animal when wet with blood.
Ashton et al report in U.S. Pat. No. 3,364,200 that surgical hemostats consisting of conventional gauze pads or similar articles impregnated with a hemostatic material such as ferric chloride, thrombin or the like, have been used for many years to arrest bleeding. However, the prior art hemostats are criticized in that they cannot be left in situ in a closed wound since foreign body tissue reaction would result, this being a serious disadvantage inasmuch as removal of the hemostat from the bleeding sight would disrupt any blood clot which has formed to cause renewed bleeding. Ashton et al observed, therefore, that a vital need exists for a hemostatic material which could be left in place in a closed wound without causing serious local tissue reaction. It is also reported that improvement was provided when it was discovered that oxidized cellulose not only had hemostatic properties but also was absorbable in animal tissue. Ashton et al provide oxidized cellulose absorbable hemostats having improved stability against deterioration on storage. The oxidized cellulose is derived from wood pulp, cotton, cotton linters, ramie, jute, paper and similar materials and regenerated cellulose or rayon produced by either the viscose or Bemberg processes.
Correll's U.S. Pat. No. 2,465,357 relates to a liquid-permeable, water-insoluble, gelatin sponge having general physical characteristics of a sponge but being absorbable by animal bodies. The sponge is a porous substance which according to the disclosure, should be reasonably soft when wet and have many fine interstices in order to hold a quantity of a therapeutic agent and to discharge the same slowly or act as an efficient absorbative material for free flowing fluids in a wound area such as blood and exudates. Correll discloses preparing an aqueous solution containing gelatin and adding a small amount of formalin and thereafter beating the material for an extended period of time to produce a firm foam of substantially greater than the volume of the original solution.
The above inventions are of interest in the field of hemostasis, however, none of the patents listed above deal with the controlling of the surface electronic or electrostatic charge of the materials involved and consequently did not go to the basis of the hemostasis problem as in accordance with the present invention.
In addition to the above, a discussion of collagen sponge appears in Collagen Sponge: Theory and Practice of Medical Applications, J. Biomedical Materials Research (John Wiley & Sons, New York) Vol. 11 No. 5, September, 1977. In this article, applications of collagen as a biodegradable material is reviewed inclusive of rate of resorption and antigenicity.